Cell for the production of metals by electrolysis of fused electrolytes



Sept. 17, 1946. S ETAL 2,407,691 CELL FOR THE PRODUCTION OF 'METALS BY ELECTROLYSIS OF FUSE!) ELECTROLYTES Filed March 24,' 1939 V 2 9 \4 If 3:36 53% 1: I i 1 5' 7.- E E Z X -10 Inventors Robert Suck y Geo?- Messner By Their Affqrnysd I Patented Sept. 17, 1946 CELL Fort THE PRODUCTION or METALS BY I ELECTROLYSIS F FUSED, .ELECTR-Qr V LYTES Robert Suchy and Georg Messner, Bitterfeld, Germany; vested in the Alien Property Custodian Application March 24, 1933,, Serial No. 263,878 In Germany April 8,1938

' 3 Claims. I 1 This invention relates to improvements in cells for the production of metals by electrolysis of fusedelectrolytes...

The production of metals by the electrolysis of fused electrolytes is preferably effected in cells heated by the decomposing electric current. In such cells the liquid metal may be deposited either at the surface or at the bottom of the molten bath according to its specific gravity being lower or higher than that of the melt. Vertical cathodes suspended from above are generally used for depositing the metal at the surface, whereas when it is desired to collect the metal at the bottom of the bath, the latter is made to form the cathode, which is then substantially horizontally disposed. The latter procedure is frequently preferred when producing metals of a low specific gravity (alkali metals, magnesium, alkaline earth metals), since the electrolyte protects the easily oxidizable metal from attack by the atmosphere. In such cases the ratio of specific gravities can, if necessary, be adjusted to the desired value by adding to the electrolyte indifferent substances adapted to reduce the specific gravity of the same.

When the metal is deposited at the bottom of the fused bath, the active surface o-fthe cathode, which is formed by the collecting metal itself, gradually approaches the anode, the level of the metal constantly rising, while the thickness of the electrolyte layer is diminishing. Unless the metal is withdrawn from the cell from time to time and the electrolyte replenished, short circuiting may easily take place between the active cathode and the anode. Adjustment of the anode so as to prevent the distance between the active electrode surface from becoming too small meets with practical difficulties, and would, when electrolyzing metallic halides with liberation of halogen, be particularly troublesome to realize without impairing the purity of the halogen recovered. But even assuming that these difficulties were satisfactorily overcome, the general disadvantage of the process still remains. viz. that the bath voltage varies during electrolysis because of the varying distance between the active surfaces of the electrodes.

The main object of the present invention is the construction of a cell for the production of metals by electrolysis of fused electrolytes, the metal being deposited at the bottom of the cell, which construction will avoid the aforesaid and other disadvantages.

In the annexed drawing, the invention is i2- lustrated in a diagrammatic manner and by way of example. In the said drawing, Fig. 1 is a vertical cross-section of a cell according to the invention. Figure 2 shows a longitudinal section through the cell. Figs. 3, 4 and 5 represent, also in cross-section, different forms of construction and relative disposition of the respective electrodes.

Referring toFig. 1 of the drawing, I denotes a vat made of refractory ceramic material capable of withstanding attack by the electrolyte and the deposited metal. A cover 2 may be, if desired, disposed on the top of the cell, so as to collect gaseous products liberated at the anode, for example chlorine, an outlet therefor being provided at 3. The bottom of the vat is lined with a layer of carbon 5, which is connected to the source of current by means of current lead 5. Above the carbon layer there are disposed bars 6 of carbon or of a metal suitable for acting as the cathode. The separately movable cathode bars 6 are loosely attached to the bottom 4. The carbon anode bars 1 of the same cross section are connected by means of the current leads 8. The current leads 5 and 8 are means for cathodically polarizing the conductive bottom 4 and anodically polarizing carbon anodes I. 9 denotes the electrolyte.

When the vat is filled with the electrolyte, the current passes directly from the carbon layer 4 to the carbon anodes l, the current connection between the bars 6 and the carbon layer being by contact only. The bath voltage, which is then still relatively high, causes the electrolyte to be heated very rapidly. But as soon as metal becomes deposited at the bars 6, it collects in the troughs between such bars, and by soaking into the chinks between the barsand the carbon layer improves the contact, so that henceforth the current passes from the upper edges of the bars 6 directly to the anode I. At the same time the voltage sinks to a minimum value corresponding to the relatively small distance between the bars 5 and the anode T and remains constant henceforth. The deposited metal is withdrawn from time to time by means of taphole l I without interrupting electrolysis and without any change in the voltage.

In order to facilitate the gathering of the deposited metal in the troughs between the cathode bars, the upper surfaces thereof may be suitably shaped, e. g. in the form of a slope, as shown in Fig. 3, the anode surfaces being provided with parallel slopes in order tosecure uniformity of voltage. According to Fig. 4 the metal-collecting space may be enlarged by employing cathode bars of conical cross-section which cathode bars extend across the whole cross-section of the bath and are supported by the side-walls of the vat. A combination of the features of Figs. 3 and 4 is shown in Fig. 5, where the spaces between the anode and the cathode form a zig-zag line, an arrangement which, it has been found, has a particularly favorable effect upon the flow of the electrolyte in the cell, the electrolyte thus being prevented from becoming locally impoverished.

We claim:

1. In a cell for the recovery of metals by the electrolysis of fused metal compounds, the arrangement of electrodes comprising a conductive substantially plane bottom, conductive separately movable cathode bars spacedly disposed on and in contact with said bottom so as to form troughlik spaces adapted to collect deposited metal between each other, above said cathode bars being disposed anode bars of the same cross section, and

means for cathodically polarizing said conductive bottom.

2. In a cell for the recovery of metals by the electrolysis of fused metal compounds, the arrangement of electrodes comprising a conductive substantially plane bottom, straight conductive separately movable cathode bars disposed substantiallyin parallel on and in contact with said bottom so as to form troughlike spaces adapted to collect deposited metal between each other, above said cathode bars being disposed anode bars of the same cross section, and, means for cathodically polarizing said conductive bottom.

3. In a cell for the recovery of metals by the electrolysis of fused metal compounds, the arrangement of electrodes comprising a conductive substantially plane bottom, straight conductive separately movable cathode bars having a sloping upper surface and disposed substantially in parallel on and in contact with said bottom so as to form troughlike spaces adapted to collect deposited metal between each other, at least one anode disposed above said bars and having a lower surface running substantially parallel with the upper surface of said bars and at a predetermined constant distance therefrom, and means for cathodically polarizing said conductive bottom and anodically polarizing said anode. Y

ROBERT SUCHY. GEORG MESSNER. 

